The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The transmissions referred to above are transmissions of the type installed in motor vehicles and, in particular, transmissions equipped with a lubricant pump and having increased lubricant requirements or large amounts of heat to be dispersed, for instance when they include a friction clutch. This is above all the case with controllable transfer transmissions for all-wheel vehicles. To provide a drive of the lubricant pump which is as direct as possible, displacement pumps are advantageously used whose rotor is fixedly seated on a transmission shaft, preferably the transmission output shaft. They are usually internal gear pumps, Gerotor pumps or the like.
Such a transfer transmission having a pump rotor seated on an output shaft is known from U.S. Pat. No. 5,697,861. The pump housing there is fixedly screwed to the transmission housing. It is disadvantageous in this design that a precise installation of the pump housing is not possible due to the long tolerance chain. The consequence is poor sealing and high wear at the seal of the pressure space due to load-dependent deflection of the shaft, also on the use of especially sintered bushings, and thereby pressure loss in the pressure space and insufficient lubricant pressure in the shaft. The installation of the pump is also difficult due to the accessibility.
To remedy these disadvantages, the screw connection between the pump housing and the transmission housing was moved away from such that the rotationally fixed connection was established by a plurality of radial arms and the pump housing was sealed by O rings with respect to the cylindrical sealing surface of the transmission housing. However, the O rings do not give the pump housing sufficient radial freedom of movement to adjust itself, they constrict it, but they do give it sufficient freed of movement to be set into a wobbling movement by even the slightest excitation (eccentricity, for example). This increases the wear of the sintered bushing forming the seal of the pressure space and generates an irritating noise. In addition, displacements between the rotor and the pump housing have a disadvantageous effect. This solution is thus also not satisfactory.